Signaling-lens.



W. CHURCHILL. SIGNALING LENS. APPLICATION FILED NOV. 26, 1907. 974,123. Patented Nov.1,1910,

WITNESS/:1S I

f) fg UNrrED sTArEs PATENT oEEIcE.

WLLIAM CHURGHILL, or coENING, NEW Yoan, AssIGNon 'ro comme @Lass wonxs, or conNINo, NEW YORK, A CORPORATION or NEW Yoan SIGNALING-LENS.

Specification of Letters Patent.

Patented Nov. 1, 1910.

Application illed November 26, 1907. Serial No. 403,980.

To all whom at may concern:

Be itI known that I, WV 1 LIAAM; (lnunmnnn, a citizen of the United States, residing at Corning, in the county of Steuben and State of New York, have invented new and useful Improvements in Signaling-Lenses, of which the following is a specification.

My invention relates to improvements in lenses, especially to that type thereof which are used 1n connection with signal lanterns, it being also applicable with advantage to lenses used on automobile or locomotive headlights. In such lenses it is desirable that a beam of light of great intensity and observable fronl a distance be provided, this necessitating that the lens project the rays more lor less parallel, although in practice the difficulties of accurate a ineinent of the axis of the lens with the point or points from which the signal is to be observed renders it desirable to so design thelens that the beam thrown thereby is slightly divergent. This is accompanied by a reduction of the intensity of the illumination, which reduces the distance' at which the signal is observable, if it be attem ted to give a suilicient spread to cover a wide field, as is necessary whenthe signal is located adjacent to and is to he seen from the curve of arailway track.

To avoid as much as possible the defects above pointed out, my invention comprises a signal lens, a part of which is so calculated as to throw what is generally called a bundle of parallel rays (although as above pointed out the rays thereof are slightly divergent) and another part of which is so calculated as to Aproject a bundle of divergent (or more exactly, of more greatly divergent) rays, the latter bundle being therefore observable from a greater distance from the axis of the lens than the-,first named; and in order to prevent. the formation of a dark zone between the bundles of parallel and diverging rays, it further consists in using the central part of the lens to project the diverging rays and the outer portion of the lens to project the parallel bundles and it further consists iu the design, construction and arrangement of the lens whereby these results are accomplished as will be hereinafter more fully described and claimed.

Referring to the accompanying drawings in which corresponding parts are designated by corresponding marks of reference:

Figure 1 is a diagram illustrating the application of my invention to a Fresnel lens. Fig. 2 is a diagram illustrating the application of my present invention to a lens of the character shown in U. S. Letters Patent No. 801,766 granted Oct. 10, 1905 to the Cornin Glass Works, as assignee from myself. 4ig. 3 is a sectional view of a lens, ysuch as used in marine signals, and to which my inventionmay be applied.

My invention in its broader as ects is not confined to the general form of t e lens and is thus .ap licable both to the round form shown in ig. 1, and to various modifications thereof and to the marine 'form shown in Fig.'3. j

The lens A to which the invention is applied is of the Well known Fresnel type as applied to railroad signal lamps, thatJ is to say, it consists as shown in Fig. 1, of a cen-l tral convex portion a surrounded by zones a--a2-a3-a. Instead, however, of so constructing 'the central portion and Vthe zones that they all focus 'more or less approximately to a common point, which heretofore has in common practice been in the plane of the source of illumination, I so construct them that the central portion or bulls eye a, has its focus F as shown by dotted lines located behind the focus of the zones, whereby with a single source of illumination for all parts of the lens, the rays projected by the central bulls eye are rendered more divergent than those from the surrounding zones. With this arrangement the rays L-a, I-a, itz-a3, zP-a, etc., projected by the zones will be somewhat divergent. They may be considered as parallel as they would obviously be if the lens was optically. perfect with the source of illumination situ-I ated at the principal focal point of the zones.

The rays f-a., from the bulls eye will be divergent. While theamount of such divergence is obviously a matter of choice under the circumstances in which the lamp is to be used good results will be secured by making such angle of diver ence measured from the axial line of the ens, about 8. By usingv the bulls eye to project the dixf'ergent bundle of rays, the latter will be projected through the parallel rays, and thus a field will be produced having a strongly illuminated center surrounded by -a less strongly illuminated zone. If on the other hand, the central part of the lens is used to project the parallel rays and the zones to project the divergent rays, a field u'ill be produced similar to the above but with the outer and inner portions separated by n dark annulus.

In Fig. 2 the application of my invention to a lens such as that shown in my Patent No. 801,760 before referred to is illustrated. In this construction instead of the zones having all the same or approximately the same point offocus, as is the case in the previous form, each zone has a separate and F3, etc., located along the axis of the lens and between the lens and the source of illumination, whereby as explained in the said prior patent the effective Yarea of illumination is that included Within the projection of the lines joining such focal points and the corresponding zones and whereby at the same time the approximate parallelism of the rays projected by the zones is maintained. Indeed they are rendered less divergent than would otherwise be the case, for it must be remembered that the difficulties of manufacture of signal lenses by pressing, and spherical aberration, preclude mathematical parallelism of the rays. this case as in the previous case, bulls eye has its principal focal point F located behind the source of illumination which in this case is therefore intermediate of. the severalfoeal-points-ofV the lenses?" lt is obvious that my invention is alsov applicable to a cylindrical lens, which instead of refracting in t-Wo directions as does a spherical lens like that shown in Figs. i and 2, refracts only in one direction. Such are the lenses commonly used for marine signals, the refraction vertical plane. The manner of constructing such a lens with the different focal distances of the several parts will be readily understood from the above and from Fig. 3, it being remembered that such a lens Will not produce a eld having concentric strongly illuminated and less strongly illuminated parts such as Will be produced by a lens of Fig. 1, but one having a central band of strong illumination and a portion of illumination prod tl distinctive, that is to say in In l the central taking place in the l less strongly illuminated on the top and bottom thereof.

It should be noted that the` peculiar field uced by a railroad semaphore lens constructed as before described may be of assistance in rendering it observer to distinguish 1t from other sources of illumination which would otherwise, from their color and location, be liable to be confounded therewith. When viewed at a short range such af lens presents the apright ring of light surrounding a dark central area in the middle of which is the erect image of the illuminating flame. Having I claim and desire to secure by ent is:-d

l. The combination with a Fresnel lens,

thus described my invention, what Letters Pati (lider-ent planes and a source of illumination located between the vlens and the focal point of a part of the lens.

2. A Fresnel lens having the central .part thereof of greater focal vlength than the zones.

3. The combination With a Fresnel lens having different parts thereof focusing on different planes and a source of illumination located intermediate of the said planes. l y 4. The combination with a Fresnel lens, ,L-having-he-eentral- Apart thereof of greater' focal length than the zones, and a source of illumination located intermediate of the several foci. 5. A lens consisting of a central bulls 1 eye and concentric zones, the central bulls l eye having a greater focal length than the zones.

6. A lens of the type described having a series of zones and a central bulls eye, each .l element of which is focused upon a different point in the axis of the lenses, the central bulls eye having the greatest focal length.

WILLIAM CHURCHILL.

WM. SINCLAIRE, MARION A. WHITLOCK.

permitting the` having different parts thereof focusing on y 

